Preparation of sensitised photographic paper



United States Patent 3,447,942 PREPARATION OF SENSITISED PHOTOGRAPHICPAPER Albert Edward Harris and Frank R. Tolhurst, Ilford, Essex,England, assignors to Ilford Limited, Ilford, Essex, England, a Britishcompany No Drawing. Filed Dec. 1, 1965, Ser. No. 510,967 Claimspriority, application Great Britain, Dec. 23, 1964, 52,236/ 64 Int. Cl.G03c l/88; B32b 29/06 US. Cl. 117-4 4 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to the preparation of sensitised photographicpaper carrying a gelatino silver halide emulsion and in particular to amethod of producing such paper with improved curl characteristics.

Sensitised photographic paper is made by coating agelatino-silver-halide emulsion on to a strong paper base Web. A web ofphotographic paper after it has been coated with thegelatino-silver-halide emulsion and dried, is normally cut up in todiscrete sheets and stored in boxes. Unless very stringent precautionsare taken regarding the relative humidity of the atmosphere in which thesheets are to be stored, it is found that when the sheets are removedfrom the boxes they will exhibit face curl, that is to say the paperwill be curled towards the emulsion-coated side. This type of curl iscalled preprocessing curl and is to be distinguished from the curlusually produced after sheet material has been processed.

It is an object of the present invention to provide a method ofproducing sensitised photographic paper which reduces or eliminates suchpreprocessing curl.

According to the present invention there is provided a method ofproducing sensitive photographic paper which comprises coating one faceof a paper web with an aqueous gelatino-silver-halide emulsion, dryingthe gelatino-silver-halide emulsion coating, and thereafter contactingthe other face of the web with at least one smooth surfaced heated drum,the temperature of the drum or drums being between 100 F. (37 C.) and200 F. (93 C.) and the total contact time between any portion of the Weband the heated drum or drums being not less than 15 seconds, andthereafter cutting the web to discrete sheet form.

The preferred method for carrying out this invention comprises coatingone face of a paper Web with an aqueous gelatino-silver-halide emulsion,drying the gelatinosilver-halide coating, and then, continuously withthe coating, guiding the coated paper web on to one or more 3,447,942Patented June 3, 1969 smooth metal-surfaced heated drums rotating at aperipheral speed substantially equal to the rate of travel of the webs,so that the other face of the coated paper web contacts the peripheralsurface of the said heated drum or drums and is carried around a portionof the circumference of the heated drum or drums in close contacttherewith, the temperature of the heated drum or drums being between F.(37 C.) and 200 F. (93 C.) and the total contact time between anyportion of the web and the heated drum or drums being not less than 15:eeonds and thereafter cutting the web to discrete sheet orm.

The contact time during which any portion of the web should, for optimumresults, be in contact with the heated drum or drums depends on thetemperature. For example, if the temperature of the drum or drums is F.a total contact time of about 100 seconds is generally found desirablebut if the temperature of the drum or drums is F. only 20 seconds totalcontact time may be necessary.

It has been found possible to store sensitised photographic paper,prepared according to this invention, in sheet form in boxes for severalmonths in an atmosphere having a relative humidity of 40% without thesheet material showing any important preprocessing curl when it isremoved from the box.

In order to determine if the heating of freshly coated photographicpaper to comparatively high temperatures had any deleterious effects onthe sensitometric properties of the emulsion freshly coated IlfordChlorobromide Paper No. 2 (the word Ilford is a registered trademark)was heated to 200 F. for various lengths of time. The table below showsthat the sensitometric properties of the emulsion are not adverselyaffected.

We claim as our invention:

1. A method of producing sensitive photographic paper which comprisescoating one face of a paper web with an aqueous gelatino-silver-halideemulsion, drying the gelatino-silver-halide emulsion coating, andthereafter contacting the other face of the web with at least one smoothsurfaced heated drum, the temperature of the drum or drums being between100 F. (37 C.) and 200 F. (93 C.) and the total contact time between anyportion of the web and the heated drum or drums being not less than 15seconds, and thereafter cutting the Web to discrete sheet form.

2. A method according to claim 1 wherein the drum or drums are metalsurfaced.

3. A method according to claim 1 wherein the drum or drums are revolvingduring the time the paper is in contact with them.

4. A method of producing sensitive photographic paper which comprisescoating one face of a paper web with an aqueous gelatino-silver-halideemulsion, drying the gelatino-silver-halide coating, and then,continuously with the coating guiding the coated paper web on to one ormore smooth metal-surfaced heated drums rotating at a peripheral speedsubstantially equal to the rate of travel of the webs, so that the otherface of the coated paper web contacts the peripheral surface of the saidheated drum or drums and is carried around a portion of thecircumference of the heated drum or drums in close contact therewith,the temperature of the heated drum or drums being between 100 F. (37 C.)and 200 F. (93 C.) and the total contact time between any portion of theweb and the heated drum or drums being not less than 15 seconds and,thereafter cutting the web to discrete sheet form.

4 References Cited UNITED STATES PATENTS 12/1952 Rose 11734 11/1953 Gray117-34 12/1958 Gray 11734 1/1942 Van Derhoef et a1. 11734 1/1966 Parkin11734 US. Cl. X.R.

